Disparate Serum Thioridazine Concentrations: Liquid Chromatography versus Radioreceptor Assay

: A radioceceptor and a liquid chromatographic assay quantitating serum thioridazine and its active metabolites yielded widely disparate results. The difference between the results of the two assays was relatively random. Contrary to earlier suggestions the radioreceptor assay may not be suitable for the measurement of all neuroleptics particularly when a common reference, such as chlorpromazine, is used.